<?php
/**
 * CDataProviderIterator class file.
 *
 * @author Charles Pick <charles.pick@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright 2008-2013 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

/**
 * CDataProviderIterator allows iteration over large data sets without holding the entire set in memory.
 *
 * CDataProviderIterator iterates over the results of a data provider, starting at the first page
 * of results and ending at the last page. It is usually only suited for use with {@link CActiveDataProvider}.
 *
 * For example, the following code will iterate over all registered users (active record class User) without
 * running out of memory, even if there are millions of users in the database.
 * <pre>
 * $dataProvider = new CActiveDataProvider("User");
 * $iterator = new CDataProviderIterator($dataProvider);
 * foreach($iterator as $user) {
 *     echo $user->name."\n";
 * }
 * </pre>
 *
 * @property CDataProvider $dataProvider the data provider to iterate over
 * @property integer $totalItemCount the total number of items in the iterator
 *
 * @author Charles Pick <charles.pick@gmail.com>
 * @author Carsten Brandt <mail@cebe.cc>
 * @package system.web
 * @since 1.1.13
 */
class CDataProviderIterator extends CComponent implements Iterator, Countable
{
    private $_dataProvider;
    private $_currentIndex = -1;
    private $_currentPage = 0;
    private $_totalItemCount = -1;
    private $_items;

    /**
     * Constructor.
     * @param CDataProvider $dataProvider the data provider to iterate over
     * @param integer $pageSize pageSize to use for iteration. This is the number of objects loaded into memory at the same time.
     */
    public function __construct(CDataProvider $dataProvider, $pageSize = null)
    {
        $this->_dataProvider = $dataProvider;
        $this->_totalItemCount = $dataProvider->getTotalItemCount();

        if (($pagination = $this->_dataProvider->getPagination()) === false)
            $this->_dataProvider->setPagination($pagination = new CPagination());

        if ($pageSize !== null)
            $pagination->setPageSize($pageSize);
    }

    /**
     * Returns the data provider to iterate over
     * @return CDataProvider the data provider to iterate over
     */
    public function getDataProvider()
    {
        return $this->_dataProvider;
    }

    /**
     * Gets the total number of items to iterate over
     * @return integer the total number of items to iterate over
     */
    public function getTotalItemCount()
    {
        return $this->_totalItemCount;
    }

    /**
     * Loads a page of items
     * @return array the items from the next page of results
     */
    protected function loadPage()
    {
        $this->_dataProvider->getPagination()->setCurrentPage($this->_currentPage);
        return $this->_items = $this->dataProvider->getData(true);
    }

    /**
     * Gets the current item in the list.
     * This method is required by the Iterator interface.
     * @return mixed the current item in the list
     */
    public function current()
    {
        return $this->_items[$this->_currentIndex];
    }

    /**
     * Gets the key of the current item.
     * This method is required by the Iterator interface.
     * @return integer the key of the current item
     */
    public function key()
    {
        $pageSize = $this->_dataProvider->getPagination()->getPageSize();
        return $this->_currentPage * $pageSize + $this->_currentIndex;
    }

    /**
     * Moves the pointer to the next item in the list.
     * This method is required by the Iterator interface.
     */
    public function next()
    {
        $pageSize = $this->_dataProvider->getPagination()->getPageSize();
        $this->_currentIndex++;
        if ($this->_currentIndex >= $pageSize) {
            $this->_currentPage++;
            $this->_currentIndex = 0;
            $this->loadPage();
        }
    }

    /**
     * Rewinds the iterator to the start of the list.
     * This method is required by the Iterator interface.
     */
    public function rewind()
    {
        $this->_currentIndex = 0;
        $this->_currentPage = 0;
        $this->loadPage();
    }

    /**
     * Checks if the current position is valid or not.
     * This method is required by the Iterator interface.
     * @return boolean true if this index is valid
     */
    public function valid()
    {
        return $this->key() < $this->_totalItemCount;
    }

    /**
     * Gets the total number of items in the dataProvider.
     * This method is required by the Countable interface.
     * @return integer the total number of items
     */
    public function count()
    {
        return $this->_totalItemCount;
    }
}